JPH09329139A - Automatically aligning rolling bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To resist an automatically aligning rolling bearing against a long time use even under high fitting stress by the use of bearing steel, by cooling an inner circumferential surface later than a raceway surface when an inner ring is hardened so as to discriminate between cooling speeds, and making the vicinity of the raceway surface under a condition of compressive stress. SOLUTION: In an automatically aligning bearing, an inner ring 10 having a plural row of raceway surfaces 12 on its peripheral surface, an outer ring 20 having a spherical raceway on its inner circumferential surface, a plural row of barreled rollers 30 freely rollingly built into among the raceway surfaces 12, 22 of the inner and outer rings 10, 20, and retainers 40 by which the row of rollers 30 is kept at predetermined intervals, are made to serve as main constituent elements. Hereat, discrimination is set between cooling speeds when the inner ring 10 formed of high carbon chrome steel is hardened, and an inner circumferential surface 14 is cooled later than the raceway surfaces 12. As a result, volume expansion generated by hardening is diminished on the side of the inner circumferential surface 14 in comparison with the sides of the raceway surfaces 12, and compressive stress remains on the raceway surfaces 12. At this time, difference in hardness among the inner circumferential surface and the raceway surfaces is preferably set to HRC 5 or more. Hereby, tensile strength by fitting can be loosened, and fault due to oil film starvation can be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a self-aligning roller bearing used in dryer rolls of paper machines.

[0002]

2. Description of the Related Art Spherical roller bearings used in paper machines, etc. are used by fixing the inner ring with a tapered hole to the taper part of the roll neck with a relatively high fitting stress, and rolling repeatedly on the inner ring. Receive stress. In particular, the dryer roll support is less likely to form an oil film under the influence of high temperature steam, and smearing is likely to occur. Then, this smearing greatly affects the life of the bearing.

[0003]

In the case of a large bearing for a paper machine or the like, since the product is thick, a material having good hardenability is used in order to quench the entire inner ring with high hardness. As a result, tensile stress may finally remain on the raceway surface due to the difference in cooling rate between the inner ring surface and the inner ring. When quenching thick products so that there is no hardness difference between the surface and the interior, there is a cooling rate difference between the surface and the interior, and the interior delays, causing volume expansion due to martensitic transformation, so the tensile stress condition near the raceway surface It becomes. Residual tensile stress on the raceway is a problem because it adversely affects bearing life.

In Japanese Patent Laid-Open No. 6-307457, carburized steel (case hardening steel) is adopted as the material of the inner ring so that the inner ring can be prevented from cracking even when used under high fitting stress. However, since it requires carburizing treatment or carbonitriding treatment, the cost is increased and it is not economical.

Therefore, it is an object of the present invention to make a self-aligning roller bearing economically usable with a high carbon chrome bearing steel for long-term use even under a high fitting stress.

[0006]

In order to achieve the above object, in a self-aligning roller bearing of the present invention, the inner peripheral surface of the inner ring made of bearing steel is cooled slower than the raceway surface to cool the raceway surface and the inner peripheral surface. The cooling speed is made different so that the vicinity of the raceway surface is in a compressive stress state.

By cooling the inner peripheral surface of the inner ring slower than the raceway surface and making the cooling rates of the raceway surface and the inner peripheral surface different, the microstructure on the inner peripheral surface side is made an incompletely hardened structure. For example, the cooling rate can be made different by making one or more of the coolant supply amount, the coolant supply time, and the coolant cooling capability different between the raceway surface side and the inner peripheral surface side. As a result, the inner peripheral surface side has less volume expansion caused by quenching than the raceway surface side, and compressive stress remains on the raceway surface.

As a result, the hardness of the inner peripheral surface of the inner ring becomes lower than the hardness of the raceway surface. The hardness difference between the inner peripheral surface and the raceway surface is HRC
It is preferably 5 or more.

By adopting a low-hardenability material as the material of the inner ring, that is, low Jomini steel, the cooling rate difference between the raceway surface and the inner diameter surface is effective in making the microstructure of the inner peripheral surface an incompletely hardened structure. Act on. Although the Jomini value of the bearing steel depends on the wall thickness, it is preferably set within the range of 8/16 ″ to 12/16 ″.

[0010]

FIG. 1 shows an example of a plummer block type self-aligning roller bearing. Spherical roller bearings include an inner ring (10) having a double row raceway (12) on the outer peripheral surface, an outer ring (20) having a spherical raceway (22) on the inner peripheral surface, and inner and outer ring (10, 20). ) The double row barrel rollers (30) incorporated between the orbits (12, 22) and the cage (40) for holding the rollers (30) of each row at predetermined intervals. As an element, the outer ring (20) is fitted with the housing (60), the inner ring (10) is fitted with the taper sleeve (52) fitted with the roll (50) through the taper hole (14),
It is fixed axially with a nut (54). In addition to the structure shown, a taper portion is formed on the roll (50),
Directly to this tapered portion, the tapered hole (14) of the inner ring (10)
May be fitted.

The self-aligning roller bearing has an aligning property because the center of the outer ring raceway is aligned with the center of the bearing, and is used even when there is a tilt between the inner ring and the outer ring caused by processing of the housing or deflection of the shaft due to load. You can do it. Also,
Since it has a large ability to load radial load, axial load in both directions, and combined load of these, it is suitable for applications subject to vibration and shock loads.

2 and 3, the reference number 23076K
The results of a comparative test conducted on the inner ring of the spherical roller bearing represented by are shown below. Each test is a test piece (inner ring) heat-treated under the conditions shown in Table 1,
Table 2 shows the results.

[0013]

[Table 1]

[0014]

[Table 2] Example The inner ring in the example is made of SUJ3 and its Jomini value is 11.8 / 16 ″.

FIG. 2A is a graph showing the cross-sectional hardness distribution of the inner ring with the hardness (HRC) on the vertical axis and the distance (mm) from the raceway surface on the horizontal axis. The black circles are the plots of the hardness at a given distance from the raceway surface on the thicker side of the inner ring with tapered holes, as shown in the diagram in the figure, and the white circles are the ones from the raceway surface on the thinner side. It is a plot of hardness at a distance of. From the figure, the hardness near the raceway surface is about 61 HRC, while the hardness on the inner peripheral surface is about 55.
You can see that it is HRC.

FIG. 2B shows the residual stress (MP
FIG. 3A is a graph showing a residual stress distribution after heat treatment of a test piece with a horizontal axis representing a distance (mm) from a raceway surface. From the figure, it can be seen that the compressive residual stress state is maintained over a range of 0.5 mm from the raceway surface.

Comparative Example The inner ring of the comparative example was made of SUJ3Z1 and had a Jomini value of 14/16 ″.

FIG. 3A is a graph in which the vertical axis represents hardness (HRC) and the horizontal axis represents distance (mm) from the raceway surface, which shows the cross-sectional hardness distribution of the inner ring after heat treatment. . The black circles are the plots of the hardness at a given distance from the raceway surface on the thicker side of the inner ring with tapered holes, as shown in the diagram in the figure, and the white circles are the ones from the raceway surface on the thinner side. It is a plot of hardness at a distance of. From the figure, it can be seen that the hardness is about 61HRC almost entirely.

FIG. 3B shows the residual stress (MP
a) is a graph in which the horizontal axis shows the distance (mm) from the raceway surface, and shows the residual stress distribution after heat treatment of the inner ring. From the figure, it is almost 0 from the raceway surface to about 0.1 mm.
Although it is MPa, it can be seen that a tensile residual stress state is reached when the pressure exceeds that.

[0020]

As described above, the self-aligning roller bearing of the present invention has a different cooling rate between the raceway surface and the inner peripheral surface when quenching the inner ring made of high carbon chrome bearing steel. Since the peripheral surface is cooled slower than the raceway surface and the vicinity of the raceway surface is in a compressive stress state, the compressive stress state near the raceway surface relieves the tensile stress due to fitting and causes a lubrication failure (oil film breakage). ) Etc. can be prevented.
Moreover, the present invention can be economically implemented only by changing the heat treatment conditions without requiring additional treatment such as carburizing and quenching.

It is known that there is a proportional relationship between the quenching temperature and the amount of retained austenite, and the higher the quenching temperature, the greater the amount of retained austenite, but according to the present invention, the quenching is performed. Since the temperature is lower than in the conventional case, the amount of retained austenite is reduced, and the effect of improving secular change is also obtained.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view illustrating the structure of a self-aligning roller bearing.

FIG. 2 is a graph for explaining the example,
(A) shows the relationship between the distance from the raceway surface and hardness, (B)
Indicates the distance from the raceway surface and the residual stress distribution.

FIG. 3 is a graph for explaining a comparative example,
(A) shows the relationship between the distance from the raceway surface and hardness, (B)
Indicates the distance from the raceway surface and the residual stress distribution.

[Explanation of symbols]

 10 inner ring 12 raceway 14 taper hole 20 outer ring 22 raceway 30 barrel roller 40 cage 50 roll 52 taper sleeve 54 nut 60 housing

Claims (6)

[Claims] 1. When quenching an inner ring made of high carbon chrome bearing steel, the inner peripheral surface is cooled slower than the raceway surface by making a difference in cooling rates between the inner raceway surface and the inner raceway surface and compressing stress near the raceway surface. Spherical roller bearing used under high fitting stress, characterized by being put into a state. 2. The spherical roller bearing according to claim 1, wherein the hardness of the inner peripheral surface of the inner ring is lower than the hardness of the raceway surface. 3. The spherical roller bearing according to claim 2, wherein the hardness difference between the inner peripheral surface and the raceway surface is HRC5 or more. 4. The self-aligning roller bearing according to claim 1, wherein the steel is low Jomini steel. 5. The Jomini value of the steel is 8/16 ″ -12.
The spherical roller bearing according to claim 4, wherein the spherical roller bearing has a diameter of / 16 ". 6. The self-aligning roller bearing according to claim 1, which is for a paper machine.